It happened in the 5,000 block of St. Elmo Avenue.
Investigators say during the installation, a breaker tripped and the power turned off.
When he turned it back on, a fire started in the wiring.
It had spread to the attic by the time Chattanooga Firefighters arrived.
They got the blaze out in about 10 minutes.
No one was injured.
The damage is estimated at $4,000 dollars.